Stoker



Oct. 3l, 1944.

-c. H..s NYDER 2,361,883

STOKER Filed Jan. -30,A 1941 4 Sheets-Sheet 1 Oct. 31, 1944. c. H. simo-ERl S'IQKER med Jan, so, 1941' 4 Sheets-Sheet 2 lll/l /l/ fwd cu/Ju A RNEYV mulates.

Patented Oct. `31, 1944 UNITED STATES i PATENT oi-'r-'iciz assises e Cliiord H. snlrlexrflormnnt, Pa. l Applicationmsm(:,lElNn. 376,603

This invention relates generally to apparatus for burning solid fuel, such as stokers, and more particularly to novel retort and fire bowl construction for supporting the burning fuel and separating the ash therefrom for removal.

This invention may be conveniently applied to stokers arranged to `burnbituminouscoal and is particularly adapted to underfed stokers.

In underfed stakers, coal is fed to the retort from below bymeans of. a screw or other conveying or propelling device, and a forced draft is usually applied through the retort to the coal under and into the fire to support and accelerate combustion of the fuel. 'As the fresh or green coal is fed upwardly through the retort from below, it is preheated by the fire and hot coals thereabove. As this preheating action takes place the gases and other .natural products such as oils are driven off and the coal particles become plastic and expand and adhere together, forming pieces of coke materially larger than the original size of the coal particles. The coke is pushed up through the retort aiid falls to one side Where it lays on a horizontal floor around the outer edge of the retort where it burns very slugglshly. This coke is out of the path of the hot part of the fire and often times goes completely dead, in which case it is difficult to re-ignite. At other times considerable partially burning coke accu- In either case the coke is not consumed at the proper time to benefit the heating system. This process results in underheating at one period and overheating at another, slow accele-ration and deceleration, and waste of fuel.

When bituminous coal is being used in an underi'ed stoker the ash accumulates at the upper and outer sidesof the retort where the heat causes the ash to melt and fuse into clinkers. The clinkers must -be removed manuallyv at frequent intervals.` The attention required in removing these clinkers from the furnace often largely offsets the advantage of a stoker.

The principal object of this invention is the I provision of a method and means for preventing the formation 'of clinkers within an underfed stoker furnace'.

Another object is the provision of novel means for removing the ash from the furnace as it is formed. Y

Another object `is the provision of means for agitating the fuel and crushing partially burned' iuel particles so that it is completely burned withn a confined and self-contained zone.

Another object is to provide above the ordinary retort an auxiliaryv retort'or container, in which combustion takes place and through which fine ash is 'blown and below which heavy ash, slate,

' regardless of whether they are high coking or free burning, higir or low ash content or high or low ash fusion coals. 2

Another object `is the provision of a domestic ash removing bituminous stolzerv that can be quickly andv easily installedas a'unit in the smaller domestic furnaces, regardless of their shape and without being assembled integral with the furnace. V

Another object is the provision of means for crushing-clinkers and large pieces of slate while they are in a hot and friable state.

Another object is the provision of means for maintaining crushed fuel or coke particles inV contact with the hot fuel bed so that they may be consumed -before being discharged.

Other4 objects and advantages appear in the following description 'and claims directed to the structure of this invention.

shown in Fig. 1.

Fig. 3 is a vertical section of a furnace retort having a rotary fire pot supported thereover.

Fig. 4 is a vertical sectionof a furnace retort having an adjustable' rotary ilre pot supported thereover. Fig.. 5 isa plan view of the structure shown in Fig. 4.

Fig. 6 is a detailed isometric view of one of the novel high tuvres shown in Figs. 1 and 4.

liir.'1isaviewsimilartol'ig.ilsliowinganv extended tuyre the upper portion of the face of which slants back at a greater angle than the lower portion.

Fig. 8 is a perspective view of the rotary grate and gear. l Fig. 9 is a plan view of a rotary fire bowl having a specic internal shape.

Fig. 10 is a perspective view of the fire bowl shown in Fig. 9.

Fig. 11 is a vertical section illustrating an underfed stoker retort with the fire bowl illustrated in Figs. 9 and 10 mounted thereon.

Fig. 12 is a top plan View ofa modied form of fire bowl.

Fig. 13 is a vertical section of a lire bowlmade up of a series of superimposed sections, rotatably supported above a retort.

Referring to Figs. 1 and 2 of the drawings, the reference numeral I designates an underfed stoker arranged to be placed in the combustion chamber of a. furnace. The stoker III comprises a forced draft chamber' II which surrounds and encloses the lower half of the retort I2 and the fuel feeding passageway I3 connected thereto.

The passageway I3 contains the ordinary screw conveyor I4 for feeding the fuel from a fuel bin or auxiliary hopper to the throat I5 at the lower end of the retort. The interior of the lower section of the retort illustrated is substantially conlcal, as indicated by the wall I5, and the bottom Il' slopes from the throat I5 at the end of'the fuel passage I3 to the opposite wall, as illustrated in Fig. 1. An openingI is provided in the bottom Il for receiving the ring I8 which is provided with a circular bore for permitting the arcuate agitator i9 to reciprocate in the retort.

The agitator I9 is preferably made in arcuate form because it, simplifies the structure and operating means. It is shown as being formed integral with the lower end of the arm ZIJ which is pivoted at 2| and whichmay be reciprocated by the operating rod 22 pivotall'y secured to the arm at 23 by means of the bifurcated member 2d. When reciprocated the outer end of the agitator extends up through the lower section of the retort into the throat formed by the tuyere blocks as indicated in dotted lines in Fig. 1. This agitator ing band 32 is required. The clamping band is made up of a split band having outwardly extending ears which are bolted together.

The grate slots 3| become wider toward the under side of the grate ring to prevent small fuel or clinker particles from being caught therein.

It should be noted that the top surface of the grate ring 28 is flush with the top of the tuyere blocks 25.

A ring gear 33 is rotatably mounted on the retort in any suitable manner such as vby the is of circular cross section and displaces a considerable amount4 of coal and colte particles through the axis of the retort throat.

The inner faces of the tuyres, which make up the upper portion of the retort, continue the upwardly expanding conical Athroat of the lower retort section. There are two types of tuyre blocks shown, the low tuyres 25 and the high tuyres 2li. The low tuyres 2&5 represent the ordinary tuyres known in the art. They are hollow and receive air from the chamber i l and discharge it in a downward direction into the throat of the retort, and they are provided with hooked shaped members for locking them into position on the lower section of the retort.

The tuyre blocks 2S are preferably constructed so that they extend materially above the top of the other tuyres and are not as wide as the ordinary tuyre block. The inner sloping faces of these tuyres are provided with openings for directing air into the cenr of the retort. This tuyre block is shown ln detail in Fig. 6, which shows openings in the sides 26a and bottom 2Gb between the two integrally i'ormed hook members ZEC. A shoulder 2 is formed on the rear of these tui/'res for supporting the annular stationary grate ring 28. A threaded opening i251 is provided in the shoulder 2 for receiving the bolts 3@ which pass through the arcuately disposed grate slots 3l for securing the grate ring to the retort. 4

The grate may be made in one piece, in which case it also acts to hold the tuyre blocks in assembled relation, otherwise a tuyre block clampannular race bearing 34 which in turn is supported on spaced legs 35 disposed around the outer shell of the retort. Teeth -36 are formed on the perimetral edge of the gear 33. These teeth have a radially disposed face which is engaged by the screw 31 for driving the same. A plurality of spaced upwardly extending braces 38 are welded or otherwise secured at their lower ends to the top surface of the gear 33 and at their upper ends to the annular rotary grate 40. The rotary grate is provided with a series of arcuate grate slots 4I the opening of which increases toward the under surface of the rotary grate which lies inthe same plane as the stationary gate ring 28 but is concentrically spaced therefrom, as illustrated on the drawings. The ring gear and the rotary grate are also-illustrated in Fig. 8..

The screw 3l lies in the same horizontal plane as the gear 33 and is arranged when driven to rotate the gear and the grate ring and to convey the ashes out of the furnace away from the retort. The rotary movement of the grate and the gear carry the ashes around to the side where the screw t? is located. 'I'he cover of the conduit i2 which encloses the screw 3l stops short of the retort to provide ampley room for driving the gear 33 and for picking up the ash.

The high tuyre blocks 26 prevent coke formation from dropping oi to one side of the retort where it may burn when heat is not required or where it may lay dormant until the accumulation is such that it must be removed manually. These high tuyres hold the coke above the fuel bed and it is thus consumed at the proper time. Conditions producing coke formations of such size may occur during long off periods when the agitator is not operating and the fuel burns deep into the retort.

When the agitator is reciprocated frequently it churns andl moves the coke particles, preventing the formation of large masses of coke.

When the retort is operad at frequent intervals and the small particles of fuel, which are still burning, are spilled out between the high tuyres they are held on the grate ring where they may finish burning and the ash thereof is finally deposited on the screw 3l.

The high tuyres are equipped with openings for discharging air toward the vertical anis of the retort. Thus when the fuel bed is above the ordinary tuyres 25 it is supplied with an additional amount of air to support combustion. The forced draft from the high tuyres induces the' movement of air and gases from around the retort into the center thereof, which materially aids in supporting proper combustion at the precise time that it is needed to produce heat and also ignites any unburned gases before they pass to the ue. This novel improvement forms an important object of this invention.

The high tuyre [i3 shown in Fig. '7 is similar t0 the high tuyre 26 except that the upper' porl chimney.

tion Il of its face recedes .or slopes at a greater angle to the vertical than the lower portion 66 which has the same slope as the faces on the ordinary tuyres 25. 'I'he reason forsetting the upper face portion u farther from the vertical axis of the retort is to get it farther away from the center o f the fire which is normally the hottest part of the re and further to permit greater Figs. 4 and 5 show the flre bowl 50 being supported by the threaded posts 62 secured to the brackets 53 welded to or formed integral with the rotary grate 46. 'Thus the high tuyres 26 and the rotary grate structure shown in Figs. l and 2 are employed with the fire bowl 50. It will i be noted that the high tuyres 26 arenot uniexpansion of the fuel bed at this particular level.

The tuyres 26 and 43 are ofcourse interchangeable.

Again it is advantageous to use the tuyres Il, the faces of which have different angular slopes, to aid the movement of the ash and fuel particles making up the top fire bed. The agitator I6 the bed, and a body of looser fuel extending over4 a greater area.

In Fig. 3 an ordinary sei; of tuyre blocks 26 is shown. The ring gear 33 in this structure merely rests on the shelf 46 of the forced draft housing of the retort. A flat graphite ring 41 may be placed on the shelf 46l and a graphite collar 66 may be placed around the-tuyre blocks to reduce the friction of the gear ring 33.

The upwardly extending posts 46 are secured at their lower ends to the ring gear 33 and are arranged to support the ilre bowl 6 0. This nre bowl maybe made of any suitable heat resistant formly positioned about the axis of the retort in Iiig. 5 but are grouped around the upper side. The reason for placing these tuyre blocks in this manner is to counteract the feeding effect of the screw I4 las it tends to pile the fuel up on this side.

The tire bowl 5b shown in Figs. 4 4and 5 is provided with three pocket recesses 54 -having opposed bifurcated lugs 55 arranged to receive the narrow neck of the adjusting sleeve 56. These sleeves are each provided with a threaded bore which enables them to be raised and lowered on the threaded post 52. Since the bowl isl provided with a three point'suspension it may be readily adjusted thereon as illustrated in full and dotted lines in Fig. 4. vBy adjusting one side of the bowl higher above the stationary grate 26 than the other, the lower rim becomes spaced.

the bowl to be rotated on an eccentric path relative to the vertical axis of the retort. If the eccentricity is not great enough the lugs may be positioned at different elevations on the bowl metal or ceramic. It is preferably in the shape of an inverted frustum of a cone, the smallest diameter of which is at least as great and preferably greater than the diameter of the bell en d of the retort. The re bowl may be made in one or more pieces. When it is constructed from a ceramic material indented pockets may be formed.

on the perimetral surface for receiving the upper ends of the posts 46.

The fire bowl 51| being supported on the ring gear 33 thus rotates with the same and its lower rim is preferably spaced sufficiently above the tuyre blocks 25 as indicated by the annular opening 6l to prevent the escape of a fair sized piece of fuel. However the relative motion of the fuel particles cerated by theA agitator and the rotating bowl tumbles the ash downwardly and permits it to be discharged radially outwardly through the opening 6| where it is picked up by the ring gear 33 and carried to a suitable ash pit or bin at the side of the retort or to an ash removing screw as illustrated in Fig. 2.

The fine ash that is sufliciently light to be carried by the forced draft up through the burning fuel in the fire bowl passes out the flue or is preeipitated to the side of the retort.'

The forced draft which is discharged through the tuyre openings into the throat of the retort travels upwardly through the fire bowl. This draft of air up through the nre bowl draws gases and air from the combustion chamber in through the annular opening 5l which burns and aids in supporting the combustion of the fuel at te opening. This circulation oi-air within the combustion chamber is in the shape of anannularvortex, thereby burning a greater percent of the gaseswhich ordinarily pass out throughl the back of each high tuyre.

to render the bowl eccentric or tipped to the axisof the retort. Thus the rotary movement of the bowl through an inverted conical orbit. such as is attainable with the adjustment shown in Fig. 4, results in the crushing of the fuel particles between the lower rim of the bowl and the stationary grate 28 and between the lower inner surface ofthe bowl and the backs and sides of the high tuyres.

Because of the eccentric relation ofthe bowl to the high tuyres as the bowl is being rotated it squeezes the `fuel or clinkers while in a friable state between the inner wall and the sides and A The pieces crushed in this manner are then held by the stationary grate 26 and rotary grate 40 in direct contact with the fire for considerable time. If these crushed4 particles are combustible they are consumed, but if the particles crushed are clinkers they cannot again re-fuse because while the tire supported on the grates 26 and 4U is hot enough to consume fuel the heat is not suiliciently in-A tense to melt ash or clinker. l12efusing of the ash or clinker is also prevented because no depth .or quantity of same can accumulate on the and discharged out from under the bowl onto the grate where they are carried to the ash pit containing the ash conveyor screw. i

'I'hus the combined action of the agitator and the rotary, eccentrically disposed bowl prombte agitation and subsequent crushing of the'fuel as it is being discharged radially outwardly from a zone intermediate of the height of the flre bed supported in the retort and the rotaryflre bowl.

One advantage of having 'a rotary fire bowl above the retort is in the radial discharge of the fuel and ash particles mechanically from this intermediate zone of the fire bed' which is produced by this relative rotary movement. In most retorts the ash and fuel particles are permitted to spill out over the top of the retort. With this structure the ashes and fuel particles are not discharged over the top of the bowl and a positive motion is mechanically imparted to the ash and fuel particles which reach this zone, crushing them and forcing them to be discharged radially outwardly under the bowl in the face of an induced draft of gas and air from the combustion chamber which further and quickly supports combustion of the fuel particles.

When, the vertical and horizontal crushing` action is added to this structure the action is made more positive and the combustion speeded up at the proper time, preventing overheating, because partially burned coked fuel is not permitted to accumulate and burn when the furnace is not operating.'

In Figs. 9, and 11 a different type of rlre bowl 50 is shown. Here the fire bowl is made up in three sections 55, each section being made from the same pattern and each providing an inner arcuate surface 56 which is disposed eccentrically to the axis of the bowl at the lower end and tapering 01T to a common concentric rim 51 at the top. These sections may be made of metal, a ceramic, or metal lined with a ceramic.

One end of each section 55 is provided with the spaced eyes 58 and 59 and the other end with the spaced eyes 50 and 6| disposed at different heights than the spaced eyes 58 and 59. When the three sections are placed in assembled relation to form the bowl the spaced eyes on the adjacent ends become interleaved with the eyes in vertical alignment. The bowl is held in this alignment and the eyes are threaded down over 'the studs or posts 52 as shown in Fig. l1.' A

shoulder 62 may be provided on the studs 52 for limiting the downward movement of the bowl on the three studs. This shoulder may be formed integral with the stud or the rotary grate ring or it may be produced by the use of a collar slid down over the studs, as shown at 62 in Fig. 11. The bowl 50 is lockedin place by the nuts 64 threadably secured on the upper ends oi' the studs 52. The fire bowl may be adj'ustably supported as shown in Figs. 4 and 5.

As shown in the drawings the upper rim of this bowl is concentric to its own axis which is coincident with the axis of the retort. However the come gradually smaller as the bowl rotates, and

any clinker or fuel particles that cannot pass between the high tuyre and the bowl are either crushed or moved inwardly toward the center of the re in the bowl.

In view of the fact that the eccentric surfaces 52 are also conical there is a tendency for the fuel particles to be raised by the rolling action up along the surface of the bowl. The higher up the surface the greater the gap between the bowl and the backs of the high tuyres. However the climbing action of the fuel particles is interrupted by the sudden offset created by the abrupt recesses produced-by these eccentric arcuate surfaces. The fuel particles are thus rolled and tend t0 climb each arcuate wall surface until the particles reach the endy where the surface drops back to the next succeeding arcuate surface, and then the particles are dropped.

Only the large aggregates are crushed since the smaller particles either pass through the gap, are

raised or moved into the center of the fire.

The movement of the agitator accentuates the movement of the fuel particles, and the movement of the fuel particles promotes quick combustion at the time when heat is required. The movement of the fuel particles-also induces the sifting of the ash down through the bowl to the grate where it is discharged. The fine ash is blown out of the bowl by the forced draft. This is readily accomplished because the particles of fuel are kept loosely churning in the fire bowl and the air traveling upwardly therethrough picks up the fine ash and car-ries it along.

In the structure shown in Fig. 11 the ring gear 33 is rotatably supported by the conical rollers 65 carried by the spaced radially disposed stub shafts 66.

When a plain frusto conical bowl, such as that shown in Fig. 3, is rotatably supported above a retort having high tuyres 26, an opening 6'! may be provided adjacent the lower edge of the bowl for receiving large pieces of coke or clinkers. As the bowl rotates these pieces 0i' coke or clinker are crushed against the sides of the high tuyres and left exposed to the re where they are burned or continue to be ground up to permit their discharge through the opening 5 l In Fig. 12 the frusto conical fire bowl 56 is provided with a series of inwardly projecting ribs 88 which may be formed integral with the bowl or welded thereto. The vsides of these ribs act in the same manner as the opening 61 or inwardly projecting portions of the bowl shown in Figs. 9, 10 and 11, in crushing the coke and clinker particles against the high tuyres. Bowl structures of this character need not be placed eccentrically of the retort to produce the desired result.

The fire bowl structure shown in Fig. 13 is made up of a series of frusto conical bowl sections 1U, 1I and 12 welded or otherwise secured to the spaced standards 13 xed at their lower ends to the top surface of the rotary grate 40 and disposed so that the bowls are eccentric to the vertical axis of the retort. The diameter of each bowl section increases from the bottom to the top. Thus as the burning fuel rises in the bowl sections the fire radiates from between them. However the diameter of the lower bowl section 'I0 is materially greater than the outside diameter of the high tuyres 26.

By making each upper bowl section greater in diameter the ilre'is not permitted to burn against the under side of the bowl sections. The bowl sections are spaced relatively close together and the large coke or clinker particles cannot pass therebetween but work down tothe lower section and become crushed against the high tuyres by the eccentric movement of the bowl sections.

accuses the fuelin the retort at the same time.

As the coal is moved upward it'is preheated and coked. AThe burning fuel is pushed vertically out of the top of the retort into the vfire bowl by the new green coal fed from below. The burnixg fuel is thus held above the retort in the il Because of the positive agitation which the fuel receives both in the retort and at all points in the fire bowl, a shallow fuel bed is constantly maintained. No fuel goes over the top of the fire bowl. The fuel is burned as fast as it is fed and at the time heat is desired. During the off period coke in 4the re bowl quickly decelerates, but since it is held directly over the retort it ignites almost instantly when the stoker comes on. 'I'hus v all the fuel is kept under control at all times,

which results in control of combustion of coal not heretofore obtainable and which approaches the onand off control of the combustion of liquid and gaseous fuels. l

The alternate insertion into and withdrawal of the agitator from the retort causes a raising and lowering or breathing of the fuel in the retort and in the fire bowl. A forced draft of air blows the light ash up 4through and out of the fire bowl and into the combustion chamber o f the furnace around the outside edge of the retort. The vertical action of the' retort agitator, which raises and lowers all the fuel by displacement, combined with the rotary action of the fire bowl,

causes a separation of the ash from the fuel asl well as to maintain a loose uniform fire. A`At the same time, the displacement caused by the insertion ofthe agitator into the fuel causes a slight pressure of the fuel particles against the sides of the retort and sides of the fire bowl. This latter action pushes the ash out into the annular opening between the retort and the fire bowl. Any large pieces of slate or other material is crushed between the lfire bowl and the tuyres. The ash moves radially outwardly over the grates and the gear, which carries it around to the ash remover screw. The ash r over screw then conveys the ash from the fuma '1. In a retort of an underfed stoker of the character described, the combination of a retort section having an annular series of low tuyre blocks of uniform height .producing an upwardly flaring wall forming a throat and arranged-to receive fuel at the bottom, and a plurality `of high tuyre blocks interposed between and extending materially above the low tuyre blocks to support and confine Vthe fuel above the throat of the refine the fuel above the throat of the retort, said high tuyre blocks having openings on their inner face for directing aforced draft toward the center of the fuel thus confined, the inner faces of.said high tuyre blocks forming an upward continuation of the wall of the said retort section,

a grate ring surrounding the tuyre blocks, and

means for supporting the grate ring with its up` per surface-substantially flush with tn'e tops of the low tuyre blocks. i q

3. In a retort of an underfed stoker of the character described, the combination of a retort section having an annular series of low tuyre blocks of uniform height producing an upwardly flaring wall forming a throat and arranged to receive fuel at the bottom, a plurality of high tuyre blocks interposed between and extending materially above the low tuyre blocks to support and confine the fuel above the throat of the retort, said high tuyre blocks having openings on their inner face for directing a forced draft toward the center of the fuel thus confined, rthe inner faces of said high tuyre blocks forming an upward continuation of the wall of the said retortsection, a grate ring surrounding the tuyre blocksand supported for rotation with its upper surface substantially flush with the tops of the low tuyre blocks, and means for rotating the grate ring.

4. In' a retort of an underfed stoker of the character described, the combination of a retort section having an annular series of low tuyre blocks of uniform height producing an upwardly flaring .wall forminga throat and arranged to receive fuel at the bottom, a plurality of high tuyre blocks interposed between and extending materially above` the low tuyre blocks to support and confine the fuel above'the throat of the retort, said high tuyre blocks having openings on their inner face for directing`=a forced draft toward the center of the fuel thusfconfined, the innerfaces of said high tuyre blocks forming an` upwardv continuation of the wall of the said retort section.

' a grate ring surrounding the 4tuyre blocks and fixed relative thereto, a second grate ring concentric with and spaced outwardly from the first grate ring, and means to rotate the second grate ring.

- all of said tuyre blocks forming an upward contort. said high tuyre blocks having openings on their inner face for-directing a forced draft-toward the center-of 'the Lfuel thus confined, the inner faces of saidhigh tuyre blocks forming an upward continuation of the wall of the said retort section.

. 2. In a retort oranunderred Stoker or the chu;

acter described, the combination of a retort section having anV annular series of low tuyre blocks of uniform height producing an upwardly flaring wail forming a throat and arranged to receive fuel at the bottom, a plurality of high tuyre blocks interposed between and extending materially tinuation of thewall of the said retort section, and an auxiliary open bottom continuous annular fire bowl the internal diameter of which is at least as great as that of the upper end of the retort. and means for supporting the auxiliary fire bowl relative to the low tuyres and surrounding the high tuyres to provide an annular gap for the induction of air and the discharge of ash between the auxiliary fire bowl and the retort.

6. In an underfed stoker of the character dem 'I scribed. the combination of a retort section having an upwardly flaring wall forming an enclosed throat and arranged for receiving fuel at the bottom, 4an annular series of low tuyre blocks of uniform height supported by said retort section, a plurality of high tuyre .blocks interposed between the low tuyre blocks, Athe inner faces of all of 4 M said tuyre blocks forming an upward continu- We the 10W tuyre blocks to support and con.. I5 ation of the wall of the said retort section, an

auxiliary open bottom continuous annular fire bowl the internal diameter of which is at least as great as that of the upper end of the retort, and means for supporting the auxiliary fire bowl relative to the low tuyres and surrounding the high tuyres to provide an annular gap for the induction of air and the discharge of -ash between the auxiliary fire bowl and the retort, and means to rotate the auxiliary flre bowl.

'1. In an underfed stoker of the character described, the combination with a vertically disposed retort having an upwardly flaring wall and means for introducing fuel at the bottom of the retort, of an auxiliary open bottom fire bowl the internal diameter of which is at least as great as that of the upper end of the retort, means for supporting the fire bowl in close proximity to the retort for receiving and holding burning fuel from the throat of the retort and to provide an annular gap between the auxiliary fire bowl and the retort, and means to rotate the lire bowl, the axis of the flre bowl being tilted relative to the axis of its rotation. f

8. In an underfed stoker of the character de scribed, the combination of a retort section having an upwardly flaring wall forming an enclosed throat and arranged for receiving fuel at the bottom, an annular series of low tuyre blocks of uniform height supported by said retort section, a plurality of high tuyre blocks interposed between the low tuyre blocks, the inner faces of all of said tuyre blocks forming an upward continuation of the wall of the said retort section, an auxiliary open bottom re bowl the internal diameter of which is at least as great as that of the upper end of the retort, and means for supporting the auxiliary re bowl relative to the low tuyres and surrounding the high tuyres to receive and hold the burning fuel from the throat of the retort and to provide a gap between the auxiliary lire bowl and the tuyres, said supporting means holding the auxiliary fire bowl with its axis tilted relative to the axis of the throat, and means to' rotate the iirebowl,

9. In an underfed stoker of the character described, the combination of a retort section having an upwardly flaring wall forming an enclosed throat and arranged for receiving fuel at the bottom, an annular series of low tuyre blocks of uniform height supported by said retort section, a plurality of high tuyre blocks interposed between the low tuyreblocks, the inner faces of all of said tuyre blocks forming an upward continuation of the wall of the said retort section, an auxiliary open bottom fire bowl the internal diameter of which is at least as great as that of the upper end of the retort, and means for supporting the auxiliary ilre bowl to surround the high tuyres, means to rotate the auxiliary nre bowl, and an internal surface on said iire bowl arranged to coact with the high tuyres for crushing large 'said tuyre blocks forming an upward continuation of the wall of the said retort section, an

, auxiliaryopen bottom fire bowl the internal diameter of which is at least as great as that oi' the upper end of the retort, and means for supporting the aumliary firel bowl to surround the high tuyres, means to rotate the auxiliary nre bowl, and a plurality of internal annularly arranged surfaces in the re bowl angularly disposed to the axis of the retort and arranged to coact with the high tuyres for crushing large fuel and clinker particles between them.

11. In an underfed Stoker of the character described, the combination of a retort section having an upwardly aring wall forming an enclosed throat and arranged for receiving fuel at the bottom, an annular series of low tuyre blocks of uniform height supported by said retort section, a plurality of high tuyre blocks interposed between the low tuyre blocks, the inner faces of al1 of said tuyre blocks forming an upward continuation of the wall of the saidretort section, a frusto conical flre bowl disposed above the retort and into which the high tuyres extend, means to support the fire bowl tiltedrelative to the axis of the retort, and means for rotating the fire bowl.

l2. In a retort of an underfed Stoker of the character described, the combination of a retort section having an upwardly aring wall forming an enclosed throat and arranged for receiving fuel at the bottom, an annular series of low tuyre blocks of uniform height supported by said retort section', a plurality of high tuyre blocks interposed between the low tuyre blocks, the inner faces of all of said tuyre blocks'forming an upward continuation of the wall of the said retort section, a grate ring surrounding the tuyre blocks land ilxed relative thereto, a second grate ring concentric with and spaced outwardly from the ilrst grate ring, a frusto conical fire bowl supported by the second grate ring and disposed above the rst grate ring and into which the high tuyres extend, the axis of the fire bowl being tilted relative to the axis of the retort, and means for rotatably supporting the second grate ring.

13. In an underfed stoker of the character described comprising a retort having an upwardly flaring wall forming an enclosed throat and arrangedfor receiving fuel at the bottom, an annular series of spaced apart projections around the top of the retort extending materially thereabove to support and confine the fuel above the throat of the retort, the inner face of the projections forming a continuation of the throat, and spaced openingsthrough the wall of the inner face of the upper portion of the retort and of the projections to direct air for supporting combustion of the fuel retained by the retort and projections.

14. In an underfed stoker of the character described, the combination with a vertically disposed retort having an upwardly flaring wall forming an enclosed throat and `arranged for receiving fuel at the bottom, of a continuous annular re bowl the internal diameter of which is at least as great as that of the upper end of the throat of the retort, means for supporting the flre bowl in close y proximity and in spaced relation with the retort to receive and hold burningfuel from the throat ot the retort and to provide an annular gap therebetween, the axis of the flre bowl being out of alignment with the axis of the throat of the retort, and means for rotating the iire bowl.

15. In an underfed Stoker of the character described for installation in a furnace, the combination with a vertically disposed retort having an upwardly flaring wall forming an enclosed throat and arranged for receiving fuel at the bottom, of an auxiliary continuous annularilre bowl, means for rotatably supporting the auxiliary fire bowl in nation with a vertically disposed retort having an upwardly flaring wall forming an enclosed throat and arranged for receiving fuel at the bottom. of an auxiliary continuous annular nre bowl. means which are independently adjustable to receive and hold the burning fuel from the throat thereof. and means for rotating said auxiliary fire bowl.

17. In an underfed stoker of the charactei described for installation in a furnace, the combinafor rotatably supporting the auxiliary fire bowl in I close proximity to theA retort, from three points an auxiliary open bottom continuous annular lire bowl the internal diameter of which is at least as great as that of the upper end of the retort,

the upwardly extending wall of the auxiliary nre bowl is of suillcient height to receive and hold in confinement substantially all of the burning fuel discharged from the retort until combustion is completed, means for supporting the auxiliary 'nre bowl in close proximity to the retort to provide an annular gap between the lire bowl and the retort for the discharge of all of the ash from `the fuel bed, and means to rotate the auxiliary nre bowl to agitate the burning fuel and to facilitate the discharge of the ash.

20. In al retort of an underfed stoker, the combinatiori of a retort having an upwardly aring wall forming an enclosed throat and arranged fory receiving fuel at the bottom, a grate ring fixed tion with a vertically disposed retort having an upwardly ilaring wall forming an enclosed throat and arranged for receiving fuel at the bottom,` of

an open ended continuous annular auxiliary fire .il

bowl having its lower end circumventing the upper end of the retort, a grate. structure interposed between the retort and the lire bowl forming a door for the latter, and means for rotatably supporting theilre bowl.

18. In an underfed stoker of the character described for installation within a furnace chamber, the combination with a vertically disposed retort having an upwardly flaring walland means for introducing-fueI-at the bottom of the retort, of an auxiliary open bottom continuous annular :nre bowl the internal diameter of which is at. least l? as great as that of the upper end of the retort.

the upwardly extending wallof the auxiliary nre f' bowl being of suillcient height to receive and hold in confinement substantially all of the burning fuel discharged from the retort until combustion is completed, and means for supporting the auxiliary fire bowl in close proximity to the retort tovprovide an annular gap between the fire bowl and the retort for the discharge of al1 of the ash i from the fuel bed. 2

the combination 'with a vertically disposed retort havinganupwardlyflaringwallandmeanafor" introducing at the bottom of the retort. of

relative to and surrounding the retort, a second grate ringconcentric with and spaced outwardly from the first grate ring, means for rotatably supporting the second grate ring, an auxiliary open bottom fire bowl the internal diameter of which is at least as great as that of .the upper end of the retort, and means for supporting the auxiliary fire bowi'on the second grate ring toreceive and hold the burning fuelv from the throat of the retort and to provide an annular gap between the auxiliry ilre bowl and the first grate ring.

2l. In an underfed stoker of the character described for assemblage within a furnace, the combination with a vertically disposedretort having an upwardly flaring wall forming an enclosed throat and arranged to receive fuel at the bottom, of a plurality of segments, each segment having a wide end portion and a narrow end portion arranged for alternate connection which when installed in assembled relation producev an auxiliary continuous annular fire bowl having an odset at each'connection, the upwardly extending wall of the ilre bowl is of suilicient height to receive and hold in confinement the burning fuel discharged from the retort until combustion is completed, and means for supporting the assembled auxiliary fire bowl in close Vproximity to the retort to provide an annular gap between the fire bowl and the retort for the discharge of ash from the fuel bed. 1

4 CIJI'IORD H. BNYDER.. 

